Abstract

Even though many cities have recycling programs, a lot of trash still ends up in the dump. Find out which materials will break down and which materials won't. Will the results of this experiment change which products you often buy?

Objective

In this experiment you will test how biodegradable different materials are.

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Experimental Procedure

First decide which types of materials you are going to test. You can use any type of disposable item that is made by different brands or with different materials. You should pick something that will have at least five different samples. For this example, I am going to use different types of disposable cups.

Label one popsicle stick for each item using permanent marker.

Find a spot to bury your items that is out of the way of traffic, like near a fence, the corner of the yard, or in the garden.

Get your parents permission to dig a hole there. If they say it is okay, then dig a small trench large enough to fit all of your items in a row. For example, if I am burying 5 cups, I would dig a hole about 1 foot deep, 1 foot wide and 2 feet long.

Line the five items in a row in the trench.

Bury each item, placing the matching labeled popsicle stick in the dirt to mark each item.

Leave the items buried for at least 3 weeks, preferably 6 weeks or more. This is the most difficult aspect of the experiment because you need to plan ahead!

While you are waiting, you will need to develop some kind of a way to measure how much an item has decomposed in the ground. To do this you can develop a scale to help you assign number values to your data. For example, one type of scale might rate the materials from 1 to 10 depending upon how much material was left:

1

2

3

4

5

6

7

8

9

10

No degradation, all material still there

Material is soft but whole

Few holes

Some holes

More holes

About half of the material is gone

Many holes

Large tears, material is falling apart

Scraps of material left

Fully degraded, no material present

When time is up (you will want to keep track of the time buried using a calendar), go out with your shovel to dig up your items one at a time. As you dig up each item, rate the item according to the scale you developed. Record your data in a data table:

Number

Item Description

Rating

1

2

3

4

5

When you are finished you will want to make a graph of your data. Make a bar graph by writing your scale on the left side (Y-axis) and drawing a bar for each type of material. Remember to label and color code the bars of your graph.

Which materials degraded the most? The least? Which materials will break down best in a landfill? Which materials do you think we should buy?

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Variations

In addition to being biodegradable, many materials are compostable. Kitchen waste, paper products, and wood products are examples of things that can be used in a compost pile to make fertile, nutrient rich soil. Do an experiment composting different materials. Compare and contrast different methods of composting: open vs. closed, covered or uncovered, with or without turning, with or without watering. You can also experiment with vermiculture, or worm composting.

Much of the trash that ends up in a landfill falls into distinct categories. Conduct a survey of a landfill and what types of things are dumped there. You can sometimes find these statistics online from your city or county landfill. Make graphs to show the frequency and distribution of different landfill materials. Which things are the most common items in a landfill? Are there any common problem materials, like tires?

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Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Related Links

If you like this project, you might enjoy exploring these related careers:

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Environmental Scientist

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